Culture of strategically pooled bovine fecal samples as a method to screenherds for paratuberculosis

Fecal samples from 733 cows in 11 dairy herds with a low prevalence of para tuberculosis were cultured for the presence of Mycobacterium avium subsp. p aratuberculosis both individually and after combining (pooling) in groups o f 5. The culture procedure was the modified Jorgensen method, which uses Na OH and oxalic acid for decontamination and modified Lowenstein-Jensen agar slants for cultivation. Pooling was performed by mixing fecal samples from 5 animals ordered by age, herein referred to as strategic pooling. Culture of individual fecal samples detected M. a. paratuberculosis infections in 4 3 of the 733 cows and 7 of 11 infected herds (herd sensitivity = 64%). Cult ure of pooled fecal samples detected M. a. paratuberculosis in 28 of 151 po oled samples representing 8 of the infected 11 herds (herd sensitivity = 73 %). Feces of the 43 culture-positive cows was included in 32 pools: of thes e 32 pools, 26 were culture positive and 6 were culture negative. In additi on to the 26 positive pools containing feces from cows that were found cult ure positive on individual fecal samples, another 2 pools were culture posi tive, although comprised of feces from cows with negative results after cul ture of individual fecal samples. From the total of 45 infected cows that w ere found (43 by individual fecal culture and an additional 2 by pooled fec al culture), individual fecal culture detected 43 of these 45 (96%), while pooled fecal culture detected 39 (87%). Culture of strategically pooled fec al samples using the modified Jorgensen method was equivalent in herd sensi tivity to the culture of individual fecal samples and is significantly less expensive.